“The chemicals were first screened in such a way that the fine and coarse materials were separated from the correctly sized materials. They were then carried on a belt conveyor to the storage bins, whence they were fed by gravity through pipes to various mixing machines. A special mixing machine was developed to mix the carbon and granules in the proper proportions for use in the canister. The mixed chemicals were then led to the canister-filling machines. There was a separate mixing machine for each filling machine, of which there were eighteen in all. “The can-filling department was laid out in six units. Each unit had a capacity of 20,000 cans per day. A system of double belt conveyors was installed to conduct empty canisters to the machines and carry away the filled ones. “Each filling operation was carefully inspected and special stops were placed on the belt conveyors so that a canister could not go to the next operation without having been inspected. Operators and inspectors were stationed on opposite sides of the belt. The chemicals were placed in the canister in three equal layers which were separated by pads of cotton wadding. The first layer was introduced from the filling machine (which delivered automatically the proper volume of chemicals), the canister was shaken to pack the chemicals tightly, the cotton baffle inserted, the second layer of chemicals introduced and so forth. On top of the top layer of chemicals were placed a wire screen and a specially designed spring which held the contents of the canister securely in place. The metal top was then fitted and securely soldered. “Each canister was tested under water for possible leaks in joints or soldering, with an air pressure of 5 lbs. per sq. in. A test was also made for the resistance which it offered to breathing, a rate of flow of air through the canister of 85 liters per min. being maintained and the resistance being measured in inches of water. “The filled canisters were then painted a distinctive color to indicate the type of filling. “FINISHING DEPARTMENT—In the finishing department, the filled canisters, were conducted down the middle of the finishing tables and assembled to masks. [Illustration: FIG. 59.] “The finished masks were then inspected, placed in unit boxes, ten to a box, and returned for the final inspection. “FINAL INSPECTION—Final inspection of the completely assembled masks was as rigid as could be devised, and was closely supervised by army representatives. Only the most painstaking, and careful women were selected for this work and the masks were examined in every detail to discover any defect that might have escaped previous inspection. Finally, each mask was inspected over a bright light in a dark booth for small pinholes which the ordinary visual inspection might not have detected.